Individuals who differ in their circadian rhythms, so-called "early birds" and "night owls", are the well-known extreme types on the spectrum of individual variations. This phenomenon of morningness-eveningness (M-E) has been studied in normal subjects, and a self-reporting M-E questionnaire developed to detect its presence and measure its degree. People with marked morning (M) or evening (E) traits have shown differences in body temperature rhythm, urinary catecholamine excretion, subjective alertness, performance, and sleep. It is not yet known if M and E types also vary in the circadian secretory rhythms of any of the adrenal hormones, such as cortisol. If the circadian secretory rhythms of cortisol were different for M and E types, would the differences in any way be related to their morningness or eveningness? If such differences do exist, it would be possible to determine a person's diurnal type by a questionnaire, and be able to predict when that person might have peak cortisol levels. It could then be determined if these individuals have times of optimal resistance to stress, and if there are times when susceptibility to stress is increased. Thus, the timing of stressful events and interventions could be manipulated to help the individual best cope with them. The purposes of this individual research training program will be to 1) describe the patterns of cortisol secretion, sleep patterns (i.e., EEGs), self-reports of sleep quality, wound healing, and activity levels in a convenience sample of M and E types of individuals, 2) compare these characteristics between M and E subjects, and 3) examine the relationships between M-E, sleep patterns, activity levels, wound healing, and cortisol values in M and E types. The research will hopefully provide the basis from which clinical intervention studies can be planned and implemented to expand this body of knowledge.